Just pushed version 0.5.1 of RdfContext<http://github.com/gkellogg/rdf_context> to GitHub and Gemcutter<http://gemcutter.org/gems/rdf_context>. This version includes a Serializer framework, including a AbstractSerializer, RecursiveSerializer and Turtle and RDF/XML serializers based on these. The RDF/XML serializer is a big improvement over the previous version, including Typed element names an RDF Container folding using parseType="collection".
RdfContext includes native Ruby parsers for RDF/XML, RDFa and N3-rdf, which includes Turtle and N-Triples. All parsers pass W3C tests (included in specs). It also includes context-aware quad store, with in-memory and SQLite3 storage models.
At some point, it will probably make sense to bring the best features of the different Ruby RDF gems together. Arto and I have discussed how we might settle on a common interface to allow the RdfContext Parsers and Serializers to work on top of the RDF gem. Stay tuned.
Gregg